368 research outputs found
Microscopic calculation of the phonon dynamics of SrRuO compared with LaCuO
The phonon dynamics of the low-temperature superconductor SrRuO
is calculated quantitatively in linear response theory and compared with the
structurally isomorphic high-temperature superconductor LaCuO. Our
calculation corrects for a typical deficit of LDA-based calculations which
always predict a too large electronic -dispersion insufficient to
describe the c-axis response in the real materials. With a more realistic
computation of the electronic band structure the frequency and wavevector
dependent irreducible polarization part of the density response function is
determined and used for adiabatic and nonadiabatic phonon calculations. Our
analysis for SrRuO reveals important differences from the lattice
dynamics of - and -doped cuprates. Consistent with experimental evidence
from inelastic neutron scattering the anomalous doping related softening of the
strongly coupling high-frequency oxygen bond-stretching modes (OBSM) which is
generic for the cuprate superconductors is largely suppressed or completely
absent, respectively, depending on the actual value of the on-site Coulomb
repulsion of the Ru4d orbitals. Also the presence of a characteristic
-mode with a very steep dispersion coupling strongly with the
electrons is missing in SrRuO. Moreover, we evaluate the
possibility of a phonon-plasmon scenario for SrRuO which has been
shown recently to be realistic for LaCuO. In contrast to
LaCuO in SrRuO the very low lying plasmons are
overdamped along the c-axis.Comment: 30 pages, 16 figures, 4 tables, 33 reference
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Diminished neural resources allocation to time processing in Autism Spectrum Disorders
Background: Interval timing, the ability to judge the duration of short events, has been shown to be compromised in Autism Spectrum Disorders (ASD). Timing abilities are ubiquitous and underlie behaviours as varied as sensory integration, motor coordination or communication. It has been suggested that atypical temporal processing in ASD could contribute to some of the disorder's symptoms, in particular motor clumsiness and difficulties in social interaction and communication. Recent behavioural investigations have suggested that interval timing in ASD is characterised by intact sensitivity but reduced precision in duration judgements.
Methods: In this study we investigated the processing of duration as compared to pitch in a group of high-functioning individuals with ASD using magnetoencephalography (MEG). 18 adolescents and adults with ASD and 18 age- and IQ-matched typically-developing control (TDC) individuals compared two consecutive tones according to their duration or pitch in separate experimental blocks. The analysis was carried out exclusively on physically identical stimuli (500 Hz tones lasting 600 ms), which served, according to instruction, as standard or probe in a Duration or Pitch task respectively.
Results: Our results suggest that compared to TDC individuals, individuals with ASD are less able to predict the duration of the standard tone accurately, affecting the sensitivity of the comparison process. In addition, contrary to TDC individuals who allocate resources at different times depending on the nature of the task (pitch or duration discrimination), individuals with ASD seem to engage less resources for the Duration task than for the Pitch task regardless of the context. Although individuals with ASD showed top-down adaptation to the context of the task, this neuronal strategy reflects a bias in the readiness to perform different types of tasks, and in particular a diminished allocation of resources to duration processing which could have cascading effect on learning and development of other cognitiv
Hadron attenuation in deep inelastic lepton-nucleus scattering
We present a detailed theoretical investigation of hadron attenuation in deep
inelastic scattering (DIS) off complex nuclei in the kinematic regime of the
HERMES experiment. The analysis is carried out in the framework of a
probabilistic coupled-channel transport model based on the
Boltzmann-Uehling-Uhlenbeck (BUU) equation, which allows for a treatment of the
final-state interactions (FSI) beyond simple absorption mechanisms.
Furthermore, our event-by-event simulations account for the kinematic cuts of
the experiments as well as the geometrical acceptance of the detectors. We
calculate the multiplicity ratios of charged hadrons for various nuclear
targets relative to deuterium as a function of the photon energy nu, the hadron
energy fraction z_h=E_h/nu and the transverse momentum p_T. We also confront
our model results on double-hadron attenuation with recent experimental data.
Separately, we compare the attenuation of identified hadrons (pi^\pm, \pi^0,
K^\pm, p and pbar) on Ne and Kr targets with the data from the HERMES
Collaboration and make predictions for a Xe target. At the end we turn towards
hadron attenuation on Cu nuclei at EMC energies. Our studies demonstrate that
(pre-)hadronic final-state interactions play a dominant role in the kinematic
regime of the HERMES experiment while our present approach overestimates the
attenuation at EMC energies.Comment: 61 pages, 19 figures, version accepted for publication in Phys. Rev.
Synchrony in psychotherapy: High physiological positive concordance predicts symptom reduction and negative concordance predicts symptom aggravation
Objective
Therapeutic alliance is often considered as a predictor for therapeutic success. This study explored dyadic synchrony of skin conductance response (SCR) during naturalistic therapeutic interactions and investigated its potential as an objective biomarker for predicting therapy effectiveness.
Methods
In this proof-of-concept study, skin conductance from both dyad members was continuously measured via wristbands during psychotherapy. Patients and therapists completed post-session reports capturing their subjective appraisal of therapeutic alliance. Additionally, patients completed symptom questionnaires. Each therapeutic dyad was recorded twice in a follow-up design. The first session of the follow-up group was assessed for physiological synchrony (Single Session Index (SSI)). Therapy outcome was captured by the difference between symptom severity scores over time.
Results
SCR synchrony significantly predicted the outcome variable of change in patients' global severity index (GSI). High positive SCR concordance was linked to a reduction in patients' GSI, while negative or small positive SSI values were linked to an increase in patients' GSI.
Conclusion
The results demonstrate the presence of SCR synchrony in clinical interactions. Skin conductance response synchrony was a significant predictor for change in patients' symptom severity index, emphasizing its potential as an objective biomarker in the context of evidence-based psychotherapy
Distant galaxy clusters in the COSMOS field found by HIROCS
We present the first high-redshift galaxy cluster candidate sample from the
HIROCS survey found in the COSMOS field. It results from a combination of
public COSMOS with proprietary H-band data on a 0.66 square degree part of the
COSMOS field and comprises 12 candidates in the redshift range 1.23 < z < 1.55.
We find an increasing fraction of blue cluster members with increasing
redshift. Many of the blue and even some of the reddest member galaxies exhibit
disturbed morphologies as well as signs of interaction.Comment: 5 pages, 5 figures, in print format, accepted for publication by A&A
Letter
The MultiSite Spectroscopic Telescope campaign: 2m spectroscopy of the V361 Hya variable PG1605+072
We present results and analysis for the 2m spectroscopic part of the
MultiSite Spectroscopic Telescope (MSST) campaign undertaken in May/June 2002.
The goal of the project was to observe the pulsating subdwarf B star PG1605+072
simultaneously in velocity and photometry and to resolve as many of the >50
known modes as possible, which will allow a detailed asteroseismological
analysis. We have obtained over 150 hours of spectroscopy, leading to an
unprecedented noise level of only 207m/s. We report here the detection of 20
frequencies in velocity, with two more likely just below our detection
threshold. In particular, we detect 6 linear combinations, making PG1605+072
only the second star known to show such frequencies in velocity. We investigate
the phases of these combinations and their parent modes and find relationships
between them that cannot be easily understood based on current theory. These
observations, when combined with our simultaneous photometry, should allow
asteroseismology of this most complicated of sdB pulsators.Comment: 9 pages, 5 figures, accepted for publication in A&A; Figure 1 at
lower resolution than accepted versio
Electron-phonon anomaly related to charge stripes: static stripe phase versus optimally-doped superconducting La1.85Sr0.15CuO4
Inelastic neutron scattering was used to study the Cu-O bond-stretching
vibrations in optimally doped La1.85Sr0.15CuO4 (Tc = 35 K) and in two other
cuprates showing static stripe order at low temperatures, i.e.
La1.48Nd0.4Sr0.12CuO4 and La1.875Ba0.125CuO4. All three compounds exhibit a
very similar phonon anomaly, which is not predicted by conventional band
theory. It is argued that the phonon anomaly reflects a coupling to charge
inhomogeneities in the form of stripes, which remain dynamic in superconducting
La1.85Sr0.15CuO4 down to the lowest temperatures. These results show that the
phonon effect indicating stripe formation is not restricted to a narrow region
of the phase diagram around the so-called 1/8 anomaly but occurs in optimally
doped samples as well.Comment: to appear in J. Low Temp. Phy
Mixed lattice and electronic states in high-temperature superconductors
Inelastic neutron scattering measurements are presented which show the abrupt
development of new oxygen lattice vibrations near the doping-induced
metal-insulator transition in La(2-x)Sr(x)CuO(4). A direct correlation is
established between these lattice modes and the electronic susceptibility (as
measured by photoemission) inferring that such modes mix strongly with charge
fluctuations. This electron-lattice coupling can be characterized as a
localized one-dimensional response of the lattice to short-ranged metallic
charge fluctuations.Comment: 4 pages, 3 postscript figures, RevTe
Bond-Stretching-Phonon Anomalies in Stripe-Ordered La(1.69)Sr(0.31)NiO(4)
We report a neutron scattering study of bond-stretching phonons in
La(1.69)Sr(0.31)NiO(4), a doped antiferromagnet in which the added holes order
in diagonal stripes at 45 deg to the Ni-O bonds. For the highest-energy
longitudinal optical mode along the bonds, a softening of 20% is observed
between the Brillouin zone center and zone boundary. At 45 deg to the bonds, a
splitting of the same magnitude is found across much of the zone. Surprisingly,
the charge-ordering wave vector plays no apparent role in the anomalous
dispersions. The implications for related anomalies in the cuprates are
discussed.Comment: 4 two-col pages, including 4 figures (2 in color); references added
and updated Final version, accepted for publication in PR
Photoproduction of phi mesons from nuclei
We investigate the consequences of possible medium modifications of the phi
meson at finite nuclear matter density on the K+K- mass distribution in
photonuclear reactions. The inclusive cross sections for K+K- pair production
are calculated within a semi--classical BUU transport model, which combines the
initial state interaction of the incoming photon with the final state
interactions of the produced particles. The effects of final state interactions
on the invariant mass distribution of the observed K+K- pairs are discussed in
detail. In addition we calculate the Coulomb correction and possible effects of
hadronic kaon potentials on the K+K- mass spectrum. Due to the large cross
sections for reactions of the final state particles with the surrounding
nuclear medium and the influence of the Coulomb potential we find no measurable
sensitivity of the observables to the phi properties at finite baryon density.Comment: revtex4, 24 page
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